Emperor penguin huddle

Emperor penguins in a huddle during
a snow-storm. Normally penguins are very territorial and will not
approach each other easily, but this behaviour is one of the ways that
emperor penguins manage to survive successfully in the depths of the
Antarctic winter. Scientific measurements and calculations have shown
that by huddling together, emperor penguins use about half the energy
that they would otherwise and would starve to death over the winter
rather than come through and raise chicks as well.

There is a constant changing of position
from the outside to the inside and during a snow storm lasting days,
the whole huddle will slowly move a couple of hundred meters or more.